1. Field of the Invention
This invention relates to the field of oil well drilling. More specifically, this invention relates to a means to drill an oil well shaft by utilizing hydraulic turbines in combination with a clam shell arrangement to self-propel the drill.
2. Description of the Prior Art
Conventional drilling apparatus utilizes long shafts or drill strings which are subject to whipping and attendant wear and friction between shaft and hole; this, coupled with viscous fluid drag (increasing as the hole gets deeper) on the drill string, can result in bottom hole power loses up to 90%. The great losses in transmitting power characteristic of the conventional drilling system result mainly from the friction between the pipe and the hole and the viscosity of the drilling fluid. Rotating speed is limited due to whipping of the drill string; torque is limited to the dynamic torsional strength of the drill pipe.
Turbine drilling has been known since the late 1800s. However, successful turbine drilling did not occur until the late 1940s and early 1950s. Russia has developed a turbine drill over the years and currently drill 80% of their wells with this type of system. The Russian turbodrill, however, is disadvantaged in that the driving force for the turbine drill is the drill pipe stem or casing pipe which lines the hole made by the turbine drill. If the need should arise to remove the turbine drill then all of the drive string must be removed before the turbine can be removed. Conventional turbodrilling units then are not independent of the pipe stem utilized to force the turbodrill down into the well. Another disadvantage is the inability to provide instrumentation necessary to evaluate the soil conditions, rock formations, etc., because of the need for the drill string to be attached to the turbodrill. The turbodrill of the present invention being self-propelled without the utilization of a drill string allows for instrumentation to monitor the conditions of the drilled hole. Another advantage of the self-contained unit of the present invention is the ability to quickly remove the turbine drill unit from the well hole without the need to remove hundreds of feet of drill string.
While turbine drilling has been known for years, no one heretofore has attempted to operate a self-propelled turbine drill without the use of a drill or casing pipe to provide the driving force for the turbine drill.